More than 5 mix/principled shaders turns material pink in material preview but not in rendered preview? No missing textures
So I changed all the Principled BSDF shaders to simple Diffuse BSDF shaders, like Craig suggested and it worked! Don't know the exact reason why it worked but I guess the Principled BSDF is too complex for putting a bunch of them in a single material. Anyway thanks for the help again.